The invention relates to a method for the detection of information expected to be present in a defined data block of the RDS data flow transmitted as a predetermined number of periodic sequential groups. The information is detected by a radio receiver which is tuned-in, one after the other, to a number of senders to be tested or monitored, and whose RDS decoder is synchronized with the RDS data flow of the respective tuned-in sender.
Radio receivers having a particular function capable of selecting the sender, in particular, car radios, have at their disposal a separate receiver part which constantly searches in the background for acknowledged senders or, when required, monitors regularly freely definable radio senders which transmit traffic announcements. When monitoring the receivable senders, the RDS information, transmitted at an increasing degree from the sender stations, is evaluated. The receivers working in the background, must permanently tune-in to many different RDS senders and evaluate the RDS data. It is often the case that only defined RDS information is of interest, for example, a broadcast or announcement identification signal by a traffic radio sender or an alternative frequency. Since this information is transmitted in defined data blocks of the RDS data flow, the particular data block is not received until after the respective tuning-in to a sender and the synchronization of the RDS decoder to the received RDS data flow.
From DE 35 10 562 C2, a method is known for retrieving the RDS data flow, as well as, a RDS demodulator for carrying out this method. Here, the RDS demodulator actually attains an excellent safety against disturbances or noise however, the RDS decoder which follows on from the demodulator, requires a considerable time to lock-in to the RDS data flow due to the fact that information on the phase relation of the Radio Data System (RDS) data flow is neither made available by the demodulation nor by the decoding. The more often the frequency must be changed in order to identify or to check different senders, the more time is lost for the respective necessary synchronization of the RDS decoder with the RDS data flow. The time necessary for the synchronization, as well as, the time interval required until the information expected in a defined data block appears, is therefore not made available for other activities. For example, should a traffic radio sender be monitored for the existence of an announcement identification signal (TE), then each time only a single Bit in the B-block of the RDS data flow is to be evaluated. From the tuning-in of a particular traffic radio sender via the synchronization of the RDS decoder until the appearance of the searched for B-block, whose position in the received RDS data flow is not known beforehand, a time interval of more than 100 msec. can have expired. However, for evaluation of the B-block alone, a time interval of no more than 20 msec. is sufficient.
The object of the invention is to provide a method for aimed detection of information in the RDS data flow with which, the greatest portion of the time, needed up until now, for the synchronization and for binding the data block, is spared and is made available for other activities.